Centrifugal fan



(No Model.)

W. J. BALDWIN. GBNTRIPUGAL PAN.

No. 556,453. l Patented Mar. 17, 1896.

ANDREW HGRANAM.PNDYUTNQWASBINGIDMRC.

UNITED STATES PATENT OFFICE.

VILLIAM J. BALDlVIN, OF BROOKLYN, NEWT YORK.

CENTRIFUGAL FAN.

SPECIFICATION forming part of Letters Patent N o. 556,453, dated March17, 1896.

Application filed February 19, 1895. Serial No. 539,028. (No model.)

To all whom t may concern:

Be it known that l, XVILLIAM J. BALDWIN, a citizen of the United States,and a resident of the city of Brooklyn, in the county of Kings and Stateof New York, have invented certain new and useful Improvements inCentrifugal Fans, of which the -following is a specification.

Myinvention relates to improvements in centrifugal fans, and the objectof the improvement is to increase the efficiency of the fans byproviding them with a deflectingshell around the outer edges of theblades, by which the air is deflected from a direction tangential to theaxis of rotation to a direction parallel thereto, and this shell ispreferably combined with a cone around the axis of rotation to providean easy passage for the air through the fan.

As is well understood, centrifugal fans first receive the air by acentral orifice into the spaces between the blades and then by therevolution of the fan put that air into rapid rotary motion. The airthus rotated acquires a centrifugal tendency depending on the velocityof rotation, and in the common type of fan flows from the spaces betweenthe blades in a direction tangential to the rotation.

The efficiency of the centrifugal fan is theoretically very high; but itis much reduced in practice by the fact that the air after issuing fromthe fan has to be turned to a direction at right angles to its originaldirection, because the limits on the space allotted to the fan inbuildings and other conditions of its practical operation preventsetting the fan in such position that its tangents coin cide with thedirection in which the air must be delivered. l-Ieretofore the air hasbeen thus changed in direction by causing it to strike a fixed wall ofthe chamber adjacent to the fan, by which the air is turned to adirection parallel to the axis; but the losses due to the friction ofthe air-currents striking at a high velocity against a rough fixedsurface and to the back-pressures, eddies and breaking up and confusionof the air-currents are very large and seriously reduce the efficiencyof the fan.

It is the purpose of this invention to substitute for the fixed wall adeflecting-shell which forms a part of the fan and revolves with it. Theeffect now is that `in place of the air-currents striking a fixedsurface a thin layer of condensed air forms against the inner surface ofthe shell when once the air has attained the velocity of rotation of thefan, which layer itself flows steadily outward over the surface of theshell, and the main body of the air in the spaces between the bladesslides by this layer with very little friction, while eddies arepractically overcome. The result is that such a fan possesses anefficiency much in excess of ordinary cen trifugal fans. Thisdeflecting-shell in centrifugal fans is the essential element of myinvention.

Referring to the drawings which accompany the specification to aid thedescription, Figure lis a vertical section through the axis of the fan,but showing the shaft and cone in elevation. The arrows show the courseof the air. Fig. 2 is an elevation of the delivery side of the fan. Fig.3- is a top View of the fan, the upper half of the shell being removedto show the slope of the blades.

d is the shaft, turning in bearings and driven in any suitable manner;b, a vertical disk iixed on the shaft d. The diameter of said disk b isless than the extreme diameter of the fan. A cone e, preferably withconcave slope, as shown, is xed on the inlet side of the disk b, theshaft a passing through said cone. A deflecting annular shell c, open atfront and back, forms the periphery of the fan, being bolted -to theflanges on the outer edges of the blades d, said blades d being boltedat their inner flanges to the cone e, as is clearly shown in Fig. l. Thesaid blades CZ, as seen in elevation, Fig. 2, curve backward outwardly,and also, as seen in top view, Fig. 3, preferably curve or incline tothe direction of the axis. Thus the said blades d not only put the airin rapid rotation, but also exert on it a backward pushing action likethat of a propeller in water.

Immediately in front of the fan is arranged a Wall h, with a cylindricalair-inlet orifice the diameter of which is about equal to the diameterof the opening in the front of the shell c. A casting or frame k isfitted around the sides of the orifice i, which is preferably IOOrounded outwardly, as seen in Fig. l. Said frame 7a both provides asmooth surface for the inlet or fill and offers the means for supportingthe rods Z I, which carry the bearing j' of the shaft a.

I prefer to make the diameter of the orifice `l a very little greater inthe clear than the diameter of the disk b and to give to the shell e andto the slope of the cone e such curves that the air-passages between theblades (Z have the slope of double elbows of easy curvature, asindicated in Fig. l.

In operation when the fan is rapidly re Volved the blades d sooncommunicate to the air between them the same velocity of rotation as thefan itself has. This rotation of the air generates a centrifugal force,which causes the air to press violently outward and to 110W toward thelargest diameter of the shell o, being deflected by the slope of theshell, so that finally it issues from the spaces between the blades in adirection parallel to the axis of rotation. At the same time the outwardtendency of the air has generated a partialvacuum in the space Withinthe inner edges of the blades el, and thus air is continually drawn intothe fan through the inlet-orifice As long as the fan revolves there is acontinual flow of air through the fan.

Thile I prefer to form the cone e With concave slope and the shell cwith a curve from front to back, as shoivn, yet I can also form saidcone with a straight slope, as indicated by e', Fig. 4, and the shell asa frustuin of a cone e with straight sides, without departing from theessence of the invention.

New having described my improvements, I claim as my inventionl. Acentrifugal fan provided with a revoluble disk b at the back and ofsmaller diameter than the extreme periphery of the fan, a revolubleshell c having an air-inlet orifice in its front side and increasing indiameter from its front toits back side substantially as shown, andblades extending from the disk l) to the shell c and having theirentrance sides substantially parallel to the axis of rotation and theiroutlet sides bent backwardly and at an angle with the axis of rotation,substantially as and for the purpose described.

2. The combination in a centrifugal fan of a revoluble diskb at the backof the fan and of smaller diameter than the extreme diameter of the fan,a cone on the front side of the disk, a revoluble peripheral shell chaving openings at its front and rear sides and increasing in diameterfrom its front to its rear side, and blades d extending from the disk l)to the shell c and having their entrance sides substantially parallelwith the axis of rotation and their outlet sides bent backwardly and atan angle with the axis of rotation, substantially as and for the purposedescribed.

In testimony that I claim the foregoing as my invention I have signed myname, in presence of two Witnesses, this 4th day of February, 1805.

WILLIAM J. BALDWIN. Titnessesz BERNARD J. XVECKE, II. V. BROWN.

